Friday, 18 October 2013

Day 7: Friday

Learning to Braze

It was nearly crunchtime - I'd cut all my frame tubes to size (both on the mini bike and on the actual bike) so it could be put off no longer - very nearly time to braze them together!

Before that, however, it was time to braze the bottle carrier bosses to my bike's seat- and down-tubes. I went for a slightly more classy look by putting triangles under the bosses before brazing them in with silver.

Here are the finished brazes, prior to removal of flux:

That done, it was time to get on with fillet brazing practice.I started with simply brazing a couple of straight lines of brass onto a flat surface of box-section steel. It was reasonably tricky to start with partly because I'd never done it before and didn't want to burn through the steel, but partly because I found the torch a bit unweildy and it's heavy to hold in one position for a long time.After straights I tacked a couple of round sections to the box section and set about brazing them on, followed by fillet brazing the round bits I'd tacked a few days before:

After a break for lunch, I set about brazing the mini bike together. By the time I'd finished I was getting a little better at it. With a little more practice I think the actual bike will come along together nicely:

Note that we had to substitute a longer bit of tubing for the head tube as we managed to make the frame a little too big in the initial tacking.Nearly finished - note that the bottom half is done, the top half is only tacked, also note the bottle cage mount on the downtube:

Having finished it off I just need to trim that head tube down to an acceptable size and file the brazes down to make it look pretty.